Extracellular matrix (ECM) proteins play an important role in the pathological processes of tumor development and progression. Elastic Microfibril Interface Located Protein-1 (EMILIN-1), an ECM glycoprotein, has been linked to cell adhesion and migration. We previously identified from head and neck squamous cell carcinoma (HNSCC) tissues that downregulated-EMILIN-1 was associated with an increased risk of secondary primary malignancy development in HNSCC and hypothesized that EMILIN-1 functions as a tumor suppressor in HNSCC. In this study, we showed that EMILIN-1 expression in HNSCC tissues was specific to the stromal area and that secreted-EMILIN-1 level was higher in fibroblasts isolated from HNSCC tissues than in HNSCC cells. EMILIN-1 overexpression decreased cell proliferation, migration, and invasion in FaDu and CAL27 cells. Knockdown of EMILIN-1 in HNSCC cancer-associated fibroblasts (CAFs) induced cell proliferation and migration. The conditioned medium from EMILIN-1-knockdown CAFs increased HNSCC cell proliferation, and the co-culture system enhanced cancer cell migration and invasion. RNA-sequencing analysis revealed that the cell cycle and aurora kinase signaling are the most significant enrichment pathways, confirmed at the protein level. Furthermore, using an in ovo chick chorioallantoic membrane (CAM) model, overexpression of EMILIN-1 in FaDu cells reduced tumor size and Ki67-positivity and increased cleaved caspase-3 positive cells. Our findings suggest that EMILIN-1 suppresses HNSCC growth partly through the downregulation of cell cycle and aurora kinase signaling pathways.
Read full abstract